Aging, stress relieving and stablising blocks

[Mr Revhead]

tech.
you may risk damage of part due to the ductile to brittle transformation (think titanic)

you mean if you smack it with a lump of ice youll shag it?

btw, good write up.

[oldcorollas]

i meant more that if it is cold, and goes thru the transformation, you sure as hell don't want to drop it and the forces present as residual stress might even break it!!

but.. whatever floats your boat (or doesn't as the case may be )
i haven't seen the movie btw

[30psi 4agte]

FWIW: When my rods were prept for there tour of duty They were sent by the machine shop to somewhere in victoria to be sonicly relieved after they had been shot peened.( the shot peen process can aparently cuase some stress in the rods from altering the surface) Which is what 6boost is talking about.

As for doing a whole block with this process.... im not sure if it is possible.

I can find out the name of the place that did it if anyone is keen.

[Billzilla]

my guess is that heating block for a fairly long time, at a modest temperature, before machining, will lead to a more stable block in service.

i don't think that leaving a block outside will have much, if any, effect, and that it was probably a tale spun by BMW and others at the time, or perhaps the word "seasoning" got confused over time with the conditions for seasoning of wood, which is indeed leaving it outside (or at controlled temperature and humidity).

Nah it's legit.
But for sure, a prologed & controlled heating of the block will produce more reliable and predictable results.

FWIW, it's not uncommon for lathe makers to cast the beds, then leave them out in the fields for six months or so, rusting away. Then they're taken back and machined true.
They apparently stay more accurate that way.

[oldcorollas]

fair enough
i suppose it is not unexpected with an unstable material like steel or iron
there will be some amount of relaxation naturally, regardless of temperature, but that is somewhat dependent on the way the material was processed.... i was assuming a good casting process with not much residual stress... for a crappily designed casting/block, it might do wonders

i reckon the lathe makers would be better off employing or consulting a metallurgist

[30psi 4agte]

i was assuming a good casting process with not much residual stress... for a crappily designed casting/block, it might do wonders

lol
Well ...They were doin this back in the hot rod days........ so it prob made alot of difference back then, When casting technology was more primitive .

[NoRecall]

for a crappily designed casting/block, it might do wonders

Alas, they must still use this down in the Holden camp..... Well you did say it was when casting technology was primitive... Or was that when engines were primitive?

[oldcorollas]

let me clarify

when a cast item cools after casting it MUST contract. this can lead to significant stresses and if a part is designed poorly, completely warp out of shape.

how much the contractions cause a problem depends on the thickness of the casting (thicker on older blocks), the physical shape of the block (and if it has been designed in such a way as to mitigate these issues), and lastly, and perhaps most importantly, how it is cooled.
cool too quickly, or cooling unevenly can make a big difference. also, most parts are heat-treated to some degree directly after casting anyway..
it is these things that make a block more "primitive"
casting technology has come a long way over the years.

any "natural seasoning or stress relaxing" that is going to happen will happen within X amount of time after the block was first cast. taking a 20 year old block and leaving it outside will not achieve anything, whereas for a new block, perhaps the first X months will yield changes. however, this natural amount of relief directly after casting (and after the production heat treating) may be small, and would he helped by a better heat treatment directly after casting....

it owuld be interesting to see some actual tests done on "natural seasoning" by leaving outside, on an old block, to see if it makes any differences... (apart from the "i did it, and the bores didn't warp, so therefore it helped" )

[Billzilla]

http://www.youtube.com/watch?v=QsmiI...elated&search=

Problem solved - Just machine your alloy V8 block with a 5-axis milling machine, from a huge chunk of alloy.
(Eleven gorgeous minutes of video there)